1. Field of the Invention
The present invention relates generally to automotive power generators, and more particularly, to a regulator for eliminating noises generated by an automotive power generator.
2. Description of the Related Art
Because people's requirement for the car has evolved from basic transportation to comfortableness, safety, gasoline-saving, and environmental protection, electronic apparatuses mounted on the car become more and more precise and diversified. Relatively, more electronic apparatuses require greater power source. Thus, the power generator of the car equipped with those electronic apparatuses must focus on power enhancement and stability of power source.
In view of above, the power generator that is the primary element of the automotive power generating system must be designed different from the conventional one, while the kinetic energy is transformed into the electric energy, to attain the power enhancement and stability of the power source.
FIG. 6 shows a conventional voltage regulator. When a voltage Vb at a point B runs beyond a predetermined value, a Zener diode ZD1 collapses to enable conductance of a transistor Q1 and to further deactivate a semiconductor power element PTR. Thus, the current fails to flow through a field coil 79 of the power generator so that none of any magnetic field will be generated and the power generator will not generate any electric energy. On the contrary, when the voltage Vb is lower than the predetermined value, the Zener diode ZD1 will not collapse to deactivate the transistor Q1 and to enable conductance of the semiconductor power element PTR, thus enabling the power generator to generate the electric energy.
It is necessary to amplify the magnetic field for greater power output of the power generator. To amplify the magnetic field, it is also necessary to amplify the current of the field coil, and meanwhile, the semiconductor power element PTR has to endure greater current. However, the semiconductor power element PTR is composed of a Bipolar Darlington power transistor. While the field current runs beyond 5 Amperes, the Bipolar Darlington power transistor is not applicable to higher voltage drop but the metal-oxide-semiconductor field effect transistor (MOSFET) is much adapted to bear or boost heavy current.
While the MOSFET is applied to the semiconductor power element, the MOSFET is characterized by rapid voltage drop/rise during its ON/OFF switching. FIG. 7 shows a waveform comparative diagram of the voltage of a point F, i.e. a field coil, and the voltage Vb of the point B+ in a circuitry of a conventional voltage regulator. FIG. 8 shows a comparative diagram of the waveform of the point F, i.e. a field coil, and the noise waveform of the point B+ in a circuitry of a conventional voltage regulator. As indicated in FIGS. 7 and 8, , the ON/OFF switching of the semiconductor power element enables rapid voltage drop/rise, illustrating almost a plummeting/rocketing line. Thus, the MOSFET will generate greater counter electromotive force according to the formula, V=−L×(dI/dt), while applied to the voltage regulator for controlling ON/OFF of the field coil, and then the counter electromotive force will be transferred to the voltage Vb to incur more and greater power noises in the car and to cause worse quality of power supply to adversely affect the operations of electrical appliances mounted to the car. In addition, the voltage regulator itself tends to incur erroneous voltage detection because of unstable voltage Vb, such that the power generator generates super drop and rise of the output voltage.